Environ. Sci. Technol. 2007, 41, 8262–8267
Polybrominated Diphenyl Ethers in Watershed Soils of the Pearl River Delta, China: Occurrence, Inventory, and Fate M E N G - Y A O Z O U , †,‡ Y O N G R A N , * ,† J I A N G O N G , †,‡ B I - X I A N M A I , † A N D EDDY Y. ZENG† State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China, and Graduate School, Chinese Academy of Sciences, Beijing 100049, China
Received August 06, 2007. Revised manuscript received September 12, 2007. Accepted September 20, 2007.
Soils play an important role in the distribution and biogeochemical cycling of polybrominated diphenyl ethers (PBDEs) as they are a major reservoir and sink for PBDEs due to their large sorption capacity. In this study, concentrations, compositional profiles, mass inventories, and fate of Σ9PBDEs (28, 47, 66, 100, 99, 154, 153, 138, 183) and BDE 209 were investigated in 33 surface soils, six profile soils, and three pointsource polluted soils (close to e-waste dismantling sites) from the Pearl River Delta (PRD), China. The concentrations of Σ9PBDEs and BDE 209 in the surface soils ranged from 0.13 to 3.81 ng/g with an average of 1.02 ng/g and from 2.38 to 66.6 ng/g with an average of 13.8 ng/g, respectively, and ranged from 1.93 to 19.5 ng/g and from 25.7 to 102 ng/g, respectively, in the point-source contaminated soils. The PBDE compositional patterns in the surface soils indicated deca-BDE, pentaBDE, and octa-BDE products as the main sources, but those in the point-source samples suggested deca-BDE and octaBDE technical mixtures as the dominant sources. The mass inventories of PBDEs in soils of the PRD were estimated at 3.98 and 44.4 t for Σ9PBDEs and BDE 209, respectively. The average loading of PBDEs in the soils was comparable to that in the sediments of the Pearl River Estuary, suggesting that soil erosion and surface runoff are an important mode to transport PBDEs from terrestrial sources to oceans in the PRD. Individual BDE congeners, Σ9PBDEs, and PBDE 209, were significantly correlated with total organic carbon (TOC), and a good regression (except for BDE 47) between the logarithms of TOC-normalized BDE average concentrations and their log Kow was also obtained, indicating that sorption of PBDEs on soil organic matter governed their spatial distribution, transportation, and fate in the soils. Predicted aqueous and gaseous concentrations of PBDEs were derived from the soil–water and soil–air partitioning models, respectively, and good agreements were obtained between the predicted and previously reported values. BDE 47 and/or 28 did not appear
* Corresponding author phone: 86-20-85290263; fax: 86-2085290706; e-mail:
[email protected]. † Guangzhou Institute of Geochemistry. ‡ Graduate School. 8262
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 41, NO. 24, 2007
to follow the same trend for these models, an indication that an portion of them was likely the biodegradation byproducts in soils.
Introduction Polybrominated diphenyl ethers (PBDEs) are a group of additive flame-retardants that have caused considerable concern in recent years due to their increasing detectable frequency and levels in environmental compartments and humans (1–4). Categorized by the average bromine contents, three major classes (i.e., penta-BDE, octa-BDE, and decaBDE) of commercial BDE products are ubiquitously added to commercial and household products such as electrical components, plastic, paints, textiles, foam, and others (5). In China, the annual consumption of PBDEs has increased at an estimated rate of 8%, and the predominant product used is the deca-BDE technical mixture, amounting to 30000 t in 2005, followed by octa-BDE and penta-BDE. Breakdown of bulk products releases PBDEs into the environment and leads to human exposure. The fate of PBDEs in soils has not been adequately investigated. There are only a few studies on PBDEs in natural soils and electronic waste (e-waste) or sewage contaminated soils. Hassanin et al. found that the compositional profiles of 20 BDE congeners in 66 surface soils in the United Kingdom and Norway closely matched those of the penta-BDE product (7). Extremely high concentrations of PBDEs (up to 4250 ng/ g) were found in soils at an e-waste dismantling site of Guiyu, a small town in Guangdong Province of South China (8–10). The amendment of sewage sludge to soils elevated the concentrations of PBDEs by 2–13 times for sewage-sludgeamended stations or by 100–1000 times for amended/flooded farms (11). Hale et al. detected PBDEs in soils, sediments, and sewage sludge in proximity to a manufacturing building for fire retardant-treated polyurethane foam (12) and obtained ∼76 ng/g of total PBDEs in the sampling soils. Moreover, soils are a major reservoir and sink of PBDEs due to their large sorption capacity (13). The combined roles of input pathway, air-soil exchange, and degradation processes often affect the mass inventories and compositions of PBDEs in soils. The properties of soils (especially soil organic matter) and overlying vegetation as well as environmental variables can also influence the behavior and fate of PBDEs in soils (13, 14). Furthermore, the food chain transfer and bioaccumulation of PBDEs from soil–plant–animal/human in terrestrial ecological systems are an important pathway leading to human exposure. Hence investigation of PBDEs in soils can provide useful information for further understanding their environmental processes and fate. The Pearl River Delta (PRD), located in the seashore of South China, is one of the three biggest industrial regions in China and also one of the largest production sites for computers and electronic products in the world. Moreover, almost 72% of the total global e-waste is disposed and recycled in China, and Guangdong Province is the largest e-waste dismantling region in China. Illegal recycling operations of e-waste have been reported to cause severe BDE pollution (8, 10). The amount of PBDEs imported to China in the form of e-waste was estimated at 35000 t/yr, higher than the annual domestic production of brominated fire retardants (∼10000 t/year) (15). Several reports of PBDEs in environmental samples from the PRD have been published (15–19). Overall, much more information is still needed to understand the fate of these contaminants and the risk imposed from brominated flame retardants to the environment and residents of the PRD, the largest recipient of global e-waste. 10.1021/es071956d CCC: $37.00
2007 American Chemical Society
Published on Web 11/10/2007
geners in the standards were quantified in the soil samples, and BDE 85 was not quantified because of the chromatographic interferences in some of the samples. Only negligible trace concentrations of BDE 28 and 47, much lower than those in the soil samples, were detected in the procedural blank samples and were deducted from those in the samples. The average recoveries in all samples were 95 ( 16% for 13C-PCB 141 and 112 ( 17% for PCB 209. The relative standard deviation for individual BDE congeners measured in triple duplicate samples were
